Str vs atk is more complicate than that

There is no perfect gear setup since it change for every mob, food or pt setup (rng debuff, brd, dia...etc).
Since you don't know the monster def, the only way to know which one benefit the most is to use a parser and look at your average damage per hit with both. I know for exemple on weapons in the Shrine, my dmg was increased by about 0.5dmg per str points. I don't know exactly how much dmg +atk would have done in that case, but I'm pretty sure it wouldnt be anywhere close to that.
General rule I was using while xping
- Keep acc above 80% at any cost. After that, benefit from acc bonus starts decreasing. If you're spamming guillotine or any other multi hit ws, dont take off str/atk gear unless you can land every hit almost all the time
-Before 75, you probably want as much attack as you can on xp mobs (or anything above T). Unless you have a brd and someone is decreasing the monster's def, chance is benefit from atk is a lot better than str.
-After 75 in merit party, if you are dual wielding, str is almost always better. I'm not sure however for 2hand weapon since atkinfluence the average dmg between the "min" and "max". Since the range is wider, you might benefit more from atk but it's probably not always the case
You should download the parser from that link and do the test yourself. It's the only way to find which gear is better in a particular situation.
http://www.frontiernet.net/~Spyle/FFXI/ffxi.html
Oh, and go drk/war =p drk/thf is overated.
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Main: War75/Sam63/Blm71/Rng45
Sub: Nin37/Thf37/Whm37/Mnk30
Three nation: Done Zilart: Done CoP: Done